ENCePP Guide on Methodological Standards in Pharmacoepidemiology

4.4. Spontaneous report database

Spontaneous reports of adverse
drug effects remain a cornerstone of pharmacovigilance and are collected from a
variety of sources, including healthcare providers, national authorities,
pharmaceutical companies, medical literature and more recently directly from
patients. EudraVigilance is the European Union data processing
network and management system for reporting and evaluation of suspected adverse
drug reactions (ADRs). The Global
Individual Case Safety Reports Database System (VigiBase) pools
reports of suspected ADRs from the members of the WHO programme for
international drug monitoring. These systems deal with the electronic exchange
of Individual Case Safety Reports (ICSRs), the early detection of possible
safety signals and the continuous monitoring and evaluation of potential safety
issues in relation to reported ADRs. The report Characterization of databases (DB) used for signal detection
(SD) of the PROTECT project shows the heterogeneity of spontaneous
databases and the lack of comparability of SD methods employed. This
heterogeneity is an important consideration when assessing the performance of SD
algorithms.

The strength of spontaneous
reporting systems is that they cover all types of legal drugs used in any
setting. In addition to this, the reporting systems are built to obtain
information specifically on potential adverse drug reactions and the data
collection concentrates on variables relevant to this objective and directs
reporters towards careful coding and communication of all aspects of an ADR. The
increase in systematic collection of ICSRs in large electronic databases has
allowed the application of data mining and statistical techniques for the
detection of safety signals. There are known limitations of spontaneous ADR
reporting systems, which include limitations embedded in the concept of
voluntary reporting, whereby known or unknown external factors may influence the
reporting rate and data quality. ICSRs may be limited in their utility by a lack
of data for an accurate quantification of the frequency of events or the
identification of possible risk factors for their occurrence. For these reasons,
the concept is now well accepted that any signal from spontaneous reports needs
to be verified clinically before further communication.

One challenge in spontaneous
report databases is report duplication. Duplicates are separate and unlinked
records that refer to one and the same case of a suspected ADR and may mislead
clinical assessment or distort statistical screening. They are generally
detected by individual case review of all reports or by computerised duplicate
detection algorithms. In Performance of
probabilistic method to detect duplicate individual case safety
reports (Drug Saf 2014;37(4):249-58) a probabilistic method
highlighted duplicates that had been missed by a rule-based method and also
improved the accuracy of manual review. In the study, however, a demonstration
of the performance of de-duplication methods to improve signal detection is
lacking.